In this installment of our blog series on Basic Audio Techniques for Video we’ll explain how to select the right shotgun microphone for different situations on set.
If you missed the previous installment exploring how to use a boompole, you can read it here.
Just as a good camera operator carefully makes their selection between using normal, wide-angle, or telephoto lenses, a skilled sound mixer will choose from a variety of shotgun or boom microphones, depending on what works best for a specific shot. Read on as we demonstrate how to select the proper shotgun microphone for each situation.
Shotgun Mic Types
Professional sound mixers will stock their sound cart with several high quality, sensitive, condenser shotgun mics with various pickup patterns. Some will even equip themselves with specialty mics that fall in between common patterns. Mics commonly used by professional mixers include Short Shotgun (AT897), Directional Condenser (AT4051b and AT4053b), Condenser Short Shotgun (BP4073), Condenser Long Shotgun (BP4071), and Condenser Extra Long Shotgun (BP4071L).
On the consumer end of the spectrum, it’s easy to find inexpensive shotgun microphones intended to give better audio than the built-in mic found on consumer grade cameras and DSLRs. These microphones, like the AT8024, come with simple camera mounting hardware, configured with stereo mini connectors, allowing them to plug directly into consumer cameras.
For professional productions, it’s ideal to choose an electret condenser short shotgun mic, often referred to as an ENG or video shotgun. One such microphone is the AT897, which is extremely popular for newscasting, documentaries, corporate videos, and low budget productions.
Mics like the AT897 are rugged and provide balanced XLR audio output. They operate on standard phantom power or can use an internal AA battery. When using phantom power make sure no batteries are inside the unit.
Video shotgun mics have a very directional pattern, on set they are referred to as short shotguns. Shotguns provide much greater reach than typical handheld microphones. These particular microphones sound their best at no more than 3 ½ or 4 feet overhead with an ideal height of 2 to 3 feet. Moving the microphone any higher will cause the talent to start sounding thinner and more ambient.
Take care to always use a foam windscreen, even indoors, to guard against wind noise from air vents or moving the mic on a boompole.
When filming outdoors, it’s best to invest in a thicker after-market slide-on windscreen.
The majority of shotgun microphones feature a built-in switch for rolling off excess bass frequencies. This setting, known as the Low Cut switch, helps reduce wind, traffic rumble and some handling vibration.
You’ll notice a symbol that looks like a bent line; this represents low frequency roll-off. Most sound mixers use it all the time for dialogue, in the studio or on location. The only time to use the flat setting is when you’re recording music or special sound effects in a controlled environment with the microphone securely placed in a shock mount and anchored on a stand.
Condenser microphones that are used for film and TV often cost more and require phantom power from the mixer or recorder. They provide a richer sound and even greater reach.
A condenser short shotgun like the BP4073 has a pickup pattern similar to an ENG short shotgun, however it is much more sensitive. While the ENG shotgun sounds good at 3 feet overhead, the condenser shotgun sounds good at even 6 feet overhead. These microphones are most commonly used for indoor shooting.
Long shotgun mics like the BP4071 are ideal for exterior shots. These mics have an extremely tight pattern and provide the longest reach. If it is not too noisy these mics can perform at 9 feet overhead or further, both indoors and outdoors.
Long shotguns have the most side rejection, this is important when you’re battling outdoor background noise. They are even more effective if lowered closer to the actors, performing well at only 2 to 3 feet overhead.
Precision is key when using long shotguns indoors. If the boom operator’s aim is off even slightly the actor will sound noticeably off mic.
Reverberation is a common issue when using long shotgun microphones indoors. The tighter the pickup pattern of the mic the more echo it magnifies in a closed room.
With a wider pattern you actually hear less acoustic reverb. Since a wider mic has weaker side rejection along with less reach, you may end up hearing more physical background noise. To compensate, you can move the microphone closer to the talent.
Side noise is usually less of a problem than echo when filming indoors. When the time comes to shoot close ups, sound mixers switch out to a condenser cardioid boom mic like the AT4051b. This microphone has a wider pickup pattern than both a general-purpose short shotgun and long shotgun.
Place the boom mic no more than 2 feet overhead of the actor, or else the dialogue may get thinned out by ambient noise. When used at short range these microphones will make echo almost disappear while adding richness and depth to the recording.
With these tips you’ll be able to choose the right shotgun microphone for any application.